1. Field of the Invention
The present invention relates to an apparatus for printing on webs in form of individual sheets or of continuous bands, particularly--but not exclusively--textile webs.
More particularly, the invention relates to a screen- or stencil-printing apparatus.
2. The Prior Art
There are two basic types of screen-printing apparatus, the flat-screen (stencil) type and the type which uses an endless travelling screen band or belt.
A flat-screen type has been disclosed in German Allowed Application (DAS) No. 1,252,167 where the web to be printed travels between a stationary suction box and a vertically superposed, equally stationary printing-ink container. A flat screen stencil is interposed between the container and the web to produce the desired printed pattern. This apparatus requires, in addition to the printing-ink container, a squeegee which is needed to achieve a reasonably uniform distribution of the ink over the entire screen stencil. Absent the use of such a squeegee, uniform ink distribution is not to be obtained so that the printed pattern will then be non-uniform.
An endless-belt screen printing machine is known from U.S. Pat. No. 2,419,695. The screen is arranged in tubular form and rotates; located within its confines is a rotary squeegee. Located beneath the line of ink application to the web is a stationary suction device. Unlike the flat-screen type, this apparatus has relatively minor problems in respect to uniform ink distribution. In the flat-screen type of apparatus the squeegee--usually a roller squeegee--must move to and fro over the screen and ahead of it (as considered in the direction of its movement) the squeegee pushes a more or less extensive body of ink over the screen. This ink is difficult to distribute uniformly, especially over a flat screen having a large surface area, so that the printing results of flat-screen machines are often unsatisfactory.